Hydroxylated sol-gel Al2O3 as photocatalyst for the degradation of phenolic compounds in presence of UV light

Al2O3 was synthesized by the sol-gel method, dried at 100 degrees C and annealed at 400, 500, 600 and 700 degrees C, respectively. These materials were characterized and evaluated to be used as photocatalysts for the degradation of phenol in aqueous phase. Although Al2O3 is a well-known insulator, in the present study we show the feasibility of using Al2O3 synthesized by the sol-gel method as a catalyst for the photomineralization of hazardous organic molecules. The photocatalytic activity of these materials was higher than that of Degussa P-25 TiO2, and other commercial aluminas tested, particularly in the case of the sample of Al2O3 calcined at 400 degrees C. The results of Nuclear Magnetic Resonance of solids (27AlMAS NMR) indicate that Al changes its coordination number during the calcination process. Rietveld refinement of the X-ray diffraction patterns denotes a notable hydroxylation in the Al2O3 structure, which was not removed by thermal treatments. Complementary spectroscopic studies (UV-Vis and FTIR) as well as the characterization of the textural properties are reported. It is proposed that UV irradiation of the hydroxylated Al2O3 induces an effective separation of the electron-hole pairs and hence, promotes the photodegradation of phenolic compounds. (C) 2013 Elsevier B.V. All rights reserved.